Known in the art are alloy fibers of regenerated cellulose and a contained substance capable of increasing the fluid-holding capacity of rayon fibers not containing an alloying component. "Alloy rayon fiber" thus refers to a fiber formed from a uniform mixture of an aqueous alkaline cellulose xanthate solution and a substance other than cellulose as contrasted with merely coating a fiber with the substance. "Fluid-holding capacity" is a measure of liquid taken up by a mass of such alloy fibers, including the liquid held within the interstices of a mass of the fibers and the liquid absorbed and adsorbed by the fibers.
In making high fluid-holding alloy rayon, wherein viscose suitable for spinning is prepared by well-known methods, it is also known to incorporate an acrylic polymer into the viscose, and then to spin the resulting mixture to form regenerated cellulosic fiber. Representative patents describing alloy rayon containing acrylic polymers for enhancing fluid-holding capacity are U.S. Pat. Nos. 3,844,287 (now Reissue No. 30,029), 4,066,584 and 4,104,214.
Examples of teachings of copolymer systems which have absorbency utility include the following U.S. patents:
A. U.S. Pat. No. 3,567,118--Shepherd et al, issued Mar. 2, 1971, teaching the topical treatment of both natural and synthetic fibers with a solution of certain hydrophilic copolymers to aid entrapment in the fiber matrix of additives such as fragrances. The hydrophilic copolymers include copolymers of unsaturated hydroxyalkyl acrylates and monocarboxylic acids such as acrylic and methacrylic acids.
B. U.S. Pat. No. 3,669,103--Harper et al, issued June 13, 1972teaches formed articles of improved absorbency for aqueous body fluids comprising supports containing dry, solid, water-swellable, water-insoluble polymeric sorbents such as lightly cross-linked polyacrylates, poly-2-hydroxyethyl acrylates, polyvinylpyrrolidones, and acrylamide/acrylic acid copolymers. The particulate polymers are dispersed in a wood pulp slurry in a Fourdrinier paper-making machine.
C. U.S. Pat. No. 4,190,562--Westerman, issued Feb. 26, 1980, teaches a film-forming water absorbent interpolymer of copolymerizable carboxylic acids such as acrylic or methacrylic acid, acrylic esters and an acrylic nitrite or amide. Hydroxyethyl methacrylate acrylate and hydroxypropyl methacrylate are acceptable cross-linking comonomer esters.
High fluid-holding cellulosic fibers, based on the inclusion of the acrylic polymer systems commercially available, and not containing hydroxyalkyl groups, are characterized by undesirable losses to and interaction with, the aqueous acidic spin baths into which the fluid containing cellulosic and such acrylic polymers are regenerated to form alloy rayon fibers.
The spin bath usually is an aqueous solution of H.sub.2 SO.sub.4, and Na.sub.2 SO.sub.4, and sometimes contains other materials which may affect the spinning or fiber characteristics.
Such acrylic polymers lost from the cellulosic matrix during filament formation produce flocculates and/or agglomerates with spinning by-product materials. In turn, these become tacky, troublesome deposits in the spin bath system. The deposits are difficult to remove from the system and special procedures are required to deal with them.